Since a static random access memory (SRAM) is large in standby energy and high in price, cache memories using nonvolatile memories have been taken into consideration. Among the nonvolatile memories, a magnetoresistive random access memory (MRAM) has high rewriting resistance, and is capable of realizing small cell size and high integration. However, from a point of view of access speed, the SRAM is far beyond the MRAM.
Furthermore, the nonvolatile memories such as the MRAM and the like use condition varieties of configuration materials so as to retain data logics. Therefore, an occurrence rate of errors (hereinafter, error rate) becomes high due to access frequency, aged deterioration, and environmental changes such as temperatures and humidity.